1. Field of the Invention
The present invention relates to an apparatus for etching and ashing substrates such as semiconductor wafers. It also relates to a method of doing the same.
2. Description of the Related Art
A micro-pattern of an integrated circuit on a semiconductor is formed by etching an undercoat film on the semiconductor wafer while using an organic high polymer photo-resist film as its mask. The photo-resist film is removed from the surface of the semiconductor wafer after this etching process.
A plasma etching apparatus having an independent unit chamber to the etching process has been used as one of the substrate treating apparatuses.
An ashing apparatus having an independent unit chamber to the ashing process has also been used as one of the substrate treating apparatuses.
A sequence treating apparatus which is a combination of plural treatment units to achieve various functions is now in use. In the case of this sequence treating apparatus, the anisotropic etching is carried out in a main chamber, the isotropic etching (or light etching for removing damage portion of the silicon film) is then carried out in an after-treatment chamber and the ashing is finally carried out in an ashing chamber.
When it is tried to prevent the substrate from being excessively damaged at the isotropic etching and ashing processes, however, it becomes difficult to achieve a high etching rate (or high speed etching) or a high ashing rate (or high speed ashing). Therefore, the so-called batch process by which plural semiconductor wafer are treated at the same time is used to treat the wafers at low plasma current for a long time (of about 1 hour, for example).
On the other hand, it is easy to achieve a high etching rate at the anisotropic etching process because the plasma etching can be carried out using high frequency current. Therefore, the wafers are usually treated one by one.
In the case of the conventional substrate treating apparatus, therefore, the anisotropic etching step, isotropic etching step and the ashing step must be carried out by their corresponding apparatuses and the wafers to be treated must be carried between these apparatuses by hands or by automatic carriage means. This makes it necessary to carry the wafers between these apparatuses and carry them into and out of these apparatuses, thereby making low the throughput to put together all of the processes.
In addition, the wafers are contacted with atmosphere while being carried between these apparatuses. This allows dust, impurities and water in atmosphere to adhere to the wafers, thereby creating fault patterns and making the revival of treatment worse. Further, the floor space occupied by the system is increased.
Particularly when the semiconductor wafer is contacted with atmosphere while being carried from the metal etching process to the resist film removing process, a micro-amount of chlorine etching gas remaining on the semiconductor wafer reacts with water in atmosphere to corrode the metal layer on the wafer. If this corroded layer is not removed from the surface of the semiconductor wafer, therefore, the yield of semiconductor device decreases.